Why might a Pi Zero connected by USB OTG seem to disappear from the local network?

Question

The set-up

I set up a Pi Zero running Stretch Lite, and connected it via USB in OTG mode to a MacBook.

I successfully found it at raspberrypi.local from the Macintosh, was able to ssh in, install various packages and run a small Python application.

The problem

While the application was running, it seems to have dropped off the network with a broken pipe:

pi@raspberrypi:~ $ packet_write_wait: Connection to fe80::a648:c9cc:e29b:761e%bridge100 port 22: Broken pipe

Sequence of events

• MacBook: Internet Sharing was on (as it has been for weeks).
• Pi SD card was configured appropriately.
• I connected the Pi via USB to the MacBook.
• I immediately was able to ssh [email protected].
• I don't know what IP address the Pi had (I think the Mac gave it a 192.168.2.x address), but it was able to reach the Internet.
• While on the Pi, I installed various packages using apt and pip.
• I connected the servos and started using my Python application I downloaded from GitHub.
• While executing the program, which was producing output in the terminal, the Pi appeared to lose all network connectivity to the MacBook.
• The Pi continued for several minutes more until the program finished running.
• While trying to reconnect, I could no longer resolve raspberrypi.local from the Macintosh.

• The output of arp -a showed no sign of it:

  ➜  ~ arp -a   
   dsldevice.lan (192.168.1.1) at c4:ea:1d:6c:bd:ae on en0 ifscope [ethernet]
   danieles-mbp.lan (192.168.1.137) at b8:e8:56:34:97:12 on en0 ifscope permanent [ethernet]
   ? (192.168.1.255) at ff:ff:ff:ff:ff:ff on en0 ifscope [ethernet]
   ? (224.0.0.251) at 1:0:5e:0:0:fb on en0 ifscope permanent [ethernet]
   ? (224.6.7.8) at 1:0:5e:6:7:8 on en0 ifscope permanent [ethernet]
   ? (239.255.255.250) at 1:0:5e:7f:ff:fa on en0 ifscope permanent [ethernet]
   broadcasthost (255.255.255.255) at ff:ff:ff:ff:ff:ff on en0 ifscope [ethernet]
  

• After rebooting the Pi by disconnecting the power, I was once again able to reach it at raspberrypi.local.

• However, the Pi now has a 169.254.x.x address and cannot resolve host names, nor can it reach remote IP addresses.
• The Macintosh Network system preferences shows an RNDIS/Ethernet gadget attached, on a 169.254.x.x (not the one of the Pi - this is the address of that interface of the Mac).

Answer 1

169.254.x.x is a Link-local address and indicates no ipv4 address has been assigned, and will not unless you explicitly assign one.

macOS (I presume you aren't using a Macintosh) will ssh over a Link-local address, although from the error message appears to be using ipv6

I routinely ssh from macOS to my Pi and "Broken pipes" and timeouts are normal after periods of inactivity. If this concerns you you could enable keep-alive messages from the Pi.

Eventually you should be able to connect after timeout, but I usually find starting a fresh terminal session on the Mac enables a new connection to be established.